Monday, August 31, 2009

The cover of a recent issue of the avant-garde art magazine Esopus features a beautiful black-and-white image of a Crockroft–Walton generator, a familiar sight, perhaps, to deep nerds, especially those who grew up in the "age of the atom." This particular instance is from Japanese particle physics lab KEK, though the magazine also features old equipment from Fermilab. The generator was the workhorse of particle physics from the 1930s, when it was invented, into the 50s and 60s, creating the high voltages necessary to accelerate particles to high energies.

In his essay accompanying the images, photographer Stanley Greenberg quotes Art Institute of Chicago art historian James Elkins: "Particle physics images can easily be taken as art, provided they are interpreted wholly in the light of nonscientific art-world criteria." With that in mind, Greenberg also includes actual bubble chamber film, the whimsically analogue "data storage mechanism" used in particle physics in the days before computers.

Bubble chambers weren't much more than containers full of superheated (at a higher temperature than its boiling point, so that it was on the verge of boiling) liquid hydrogen, but they were the earliest particle detectors; it's hard to believe they're related to multi-story electornic monstrosities like the LHC's ATLAS detector. The bubble chamber was simple—a high-energy particle would zoom in, collide with the liquid's molecules and decay, sending of a spray of subatomic particles that caused the superheated liquid to boil as they flew through it, so that they left trails of bubbles like delicate strings of pearls. Greenberg also includes large prints of bubble-chamber images; in this new context, seem beautiful and mysterious, so much so that the images have appeared in popular culture—the Strokes' first album has bubble chamber images on its cover (above).

It's one thing to reappropriate or repurpose something that already exists. One might say it's not so different—and arguably more pleasing—than what Marcel Duchamp did with a bicycle wheel or a urinal almost a century ago. But there's another artist out there who takes the public fascination with particle physics, and its importance to the 20th and 21st century, much further than merely displaying its unappreciated relics and artifacts. Jim Sanborn takes it so far that he has split the atom—in the name of art. According to Washington Post reporter Blake Gopnik, the sculptor has established a scientific-compound-cum-studio on an island in the Potomac, and has built a real, live, working particle accelerator.

It's no LHC; it accelerates particles to high energies the good, old-fashioned way. The brushes and rollers inside a twenty-eight-foot-tall Van de Graaff generator piles charge onto its metal mushroom cap until the air ionizes. The particles discharge through the vacuum chamber of the accelerator and into the bubble chamber, where subatomic particles leave traces of their passage.

Sanborn, a sculptor and artist, has a history of getting so involved in his art that he overreaches the bounds of his field. For instance, Kryptos, his sculpture for CIA headquarters in Langley, Virginia, is an actual coded message carved in stone. Sanborn did so well that Kryptos has eluded decryption for twenty years.

I have two family members for whom a favorite topic of intellectual argument is, "But is it art?" Maybe it's the fact that I spent the weekend at an art museum with them, but, to me, Sanborn's latest work seems to raise that very question. Gopnik refers to Sanborn's island laboratory as a "studio." The Van de Graaff and accompanying vacuum components, ion gun, and bubble chamber are components of an exhibit, just as individual paintings might make up a show. But to the untrained eye it looks like a geek having some fun in his shed.

Sanborn's hardly the only amateur to have ever tinkered with particle physics. In my very first post, I mentioned that Michio Kaku, the celebrity cosmologist, built a particle accelerator in his basement at the age of seventeen. Just google "Van de Graaff" and you'll come upon the websites of amateur projects. So what makes Sanborn's island a studio, his Van de Graaff-powered accelerator a work of art?

Does the artist's intention make the work art? Sanborn's intention is clear; as Gopnik explains, the project is a recreation, almost a performance of a a piece of physics history. In the late 1920s and 1930s, physicist Merle Tuve and his team at the Department of Terrestrial Magnetism at the Carnegie Institute in Washington, D.C. were struggling to build a linear particle accelerator. By 1933, they were observing reactions at 600,000 volts, and in 1935, Tuve and company got the first results on proton-proton interactions. They were building the ground work for the atomic bomb:

A high point in scholarly exchange came in January 1939 when Niels Bohr told a conference of theoretical physicists of the discovery of uranium fission by Hahn and Meitner. Within a day the discovery was confirmed at the Department of Terrestrial Magnetism by Richard Roberts and Hafstad. Soon thereafter Roberts observed that some uranium fission events are followed by delayed emission of neutrons.

In that sense, this artwork could be seen as a prologue to Sanborn's earlier work, a set of installations inspired by the Manhattan Project. "Critical Assembly" recreated (and reimagined) experimental setups from Los Alamos in the 1940s; for "Atomic Time," Sanborn exposed film to uranium over several days until the radiation created an image. He also exposed film to old radium-dial clocks over several weeks (radium was used in the 40s and 50s because it made the dials glow.)

Assembly for Determining Critical Mass, from "Critical Assembly"

"Critical Assembly" and "Atomic Time" belong firmly to the art realm; the recreations of Los Alamos are concretely scientific, but they seem molded by an artist's hand, to have some quality of sculpture to them. But "Terrestrial Physics," as Sanborn's foray into "big science" is called, lacks to me what we might call an interpretation on the part of the artist; it would be equally at home in a particle physics lab or even a science museum.

A uranium "autoradiograph" from "Atomic Time"

Steve Brown, a NASA scientist who helped Sanborn with the delicate, finicky engineering of "Terrestrial Physics," didn't see it as art either, at first. Gopnik writes:

Brown didn't know why Sanborn wanted to achieve even that: "My initial reaction was, 'Sounds like a lot of work, and what are you going to get out of it in the end?'" Then Brown started thinking in fine-art terms, and changed his mind. "It sort of compares with an old Dutch master's painting of a kitchen table... It's a still life of something someone put a lot of energy into."

But is Sanborn's work really like the Dutch master's painting of a kitchen table? Or is it more like the Dutch master making a kitchen table, performing the carpenter?

Sanborn performs science, but "Terrestrial Physics" is not science, by which I mean that a lot of scientific knowledge and rational thinking may be going into the construction of this, but Sanborn's not going to be studying bubble-chamber film to understand the subatomic world. But at this point, it's not exactly art, either; as far as I know, Sanborn has no takers for this particular piece, although he's certainly an admired artist and sculptor. "Terrestrial Physics" is the set made real, a way of bringing us to a moment, a way of making visible not the secret world of particles but the secret world that science was in the 30s and 40s. And given how history has transpired since, those moments in front of the bubble chamber are as fundamental to who we are as the particles themselves.

Friday, August 28, 2009

When today's soldiers enter combat, they're better protected from explosions than the military personnel of any previous war. Ultra-strong helmets shield them from the flying shrapnel of homemade bombs; high-tech cushioning cradles their skulls during sudden impacts with the ground. But because modern soldiers are surviving explosions that would have taken the lives of Vietnam-era infantrymen, army hospitals are seeing a rise in a particularly painful war wound—traumatic brain injury (TBI).

TBI can range from a simple concussion to damage with long-term effects, including impaired cognitive abilities and even anxiety and depression. New research is helping to explain how those injuries come about, potentially pointing the way to helmet designs to reduce brain damage. Using code originally designed to simulate how a detonated weapon rattles a building or tank, physicists at Lawrence Livermore National Laboratory in California and the University of Rochester in New York modeled an all-too-real situation: a 5-pound bomb exploding 15 feet from a soldier's head. Their goal was to understand the effects of the high-speed shock wave that follows an explosion.

Some doctors have suggested that the wave reaches the brain through the eyes or ears; others say it causes compression of the chest and a subsequent surge of blood to the brain. The new research, soon to appear in the journal Physical Review Letters, shows that the shock wave doesn't accelerate the head enough to damage the brain. Instead, it seems to affect the skull directly.

"Your skull is not exactly rigid, so the pressure actually deforms the skull as the blast wave moves across," said Eric Blackman, who is one of the authors of the study. "That flexure drives a stress wave that propagates into the brain. It's something like an inverse earthquake."

The waves flex the skull by only about the width of a human hair. But according to coauthor William Moss, "that's enough to generate pressures in the brain comparable to [an] impact." The reason is that the brain contains a lot of water. "Push on it a little bit and you get a lot of pressure," said coauthor Michael King. Because the blast wave sweeps across the skull in just a fraction of a second, "you don't have time for the pressure to dissipate, so you get a localized region of very high pressure."

David Moore, a vascular neurologist and the deputy director of research at the Defense and Veterans Brain Injury Center, headquartered in Washington, D.C., said that the skull flexure mechanism proposed by the physicists is just one hypothesis among several competing concepts of blast waves and injury. "Like all these hypotheses there’s yet work to be done in terms of validation," he said. "There are too many unknown variables from the constitutive properties of brain and skull at high strain rates along with other associated blast phenomena."

The team considered the performance of Kevlar helmets with two kinds of cushioning systems: a nylon web system that was retired in 2003, and the foam pads of the Advanced Combat Helmet, which is standard-issue for today's soldiers. The results were unsettling.

To protect soldiers from bullets and shrapnel, modern helmet design maintains a 1.3-cm gap between helmet and head; in the simulation, the blast wave washed into the helmet through this gap. "The helmet acts as a windscoop, so the pressure between the skull and helmet is larger than the blast wave by itself," King said. While the ACH's pads mostly prevented this underwash, they also passed on forces to the skull.

King suggested that the pads' stiffness could be optimized to "take the best of both worlds; it doesn't allow the blast in there, and it doesn't transfer [forces] from the helmet to the head." He stressed that when making changes to the helmet, preserving its ability to reduce impacts and fend off bullets was paramount. "You'd have to be careful to make sure it doesn't interfere with what the helmet does very well, which is stopping fragments and bullets," he said. "The whole idea why there was a big gap between skull and helmet in the first place, is it makes it more likely for the soldier to survive if a bullet hits the helmet."

The researchers stopped short of claiming the high-pressure regions caused by blast waves would then cause TBI. But their findings seem to clear some of the fog surrounding closed head injuries, said Brent Masel, a neurologist and the president and medical director of the Transitional Learning Center, a post acute brain injury treatment program in Galveston, TX.

"We classify brain injuries as mild, moderate, or severe based on the amount of trauma they have at that time… but the severity of injury and eventual outcome may very often be different," Masel said." Assuming their model is correct, this answers one of the questions that keeps getting raised-how do these men and women who have a minor blast injury have symptoms? It may be that the blast injury isn't so minor."

According to an article in the New England Journal of Medicine, between January 2003 and February 2005 Walter Reed Army Medical Center treated more than 450 patients with traumatic brain injury. The majority of these were closed brain injuries, meaning no shrapnel had penetrated the skull. As stated in the above story, and illustrated in the NEJM article, moderate and severe TBI, which formed 59 percent of these injuries at Walter Reed, have extremely long-lasting effects. That could mean headaches and sensitivity to light; it could also mean changes we usually associate with personality, like mood changes or impulsiveness. There are also the cognitive changes, said Dr. Wayne Gordon, director of the Mount Sinai School of Medicine's Department of Rehabilitation Medicine, such as "memory, information processing speed, attention, executive functions."

"Language can be impaired, but not in the same way as a stroke patient," he said. "[Patients can have] difficulty with retrieving words... or in what we call pragmatics, understanding social communication."

Because the effects TBI are so long-lasting and complex, the cost to the government is enormous. A 2005 paper by Scott Wallsten of Stanford University and the Technology Policy Institute and Katrina Kosec of the World Bank's Development Research Group estimates that the cost of treating a soldier with serious TBI is between $600,000 and $5,000,000 over his or her lifetime.

Intriguingly, there is concrete evidence that the damage caused by a blast wave differs significantly from the damage caused by an impact. Moore recently completed a study that used diffusion tensor imaging to compare the brains of injured soldiers exposed to a blast to those of soldiers who had brain injuries due only to impacts, and also to those of healthy soldiers.

It turns out there is a difference—a parameter called the apparent diffusion coefficient was smaller for the blast victims. "That suggests to us that in these service members, there might be an aspect of what we'd term an chronic inflammatory response, tissue that's still injured [after] quite a number of days, 70 to 75 days, nearly three months," Moore said.

Thursday, August 27, 2009

Physicist German Drazer drops a ball bearing into a Lego pegboard. (Will Kirk/JHU)

WASHINGTON (ISNS) -- Researchers at Johns Hopkins University have developed an unorthodox method to study the behavior of microscopic nano-particles -- by playing with Legos.

The team, led by physicists Joelle Frechette and German Drazer, built a grid out of round Lego blocks and immersed it in liquid glycerin to observe the paths of ball bearings they dropped into the construction.

Though Lego blocks are many times larger than a nano-device, particles passing through the grid behave fundamentally the same way, the researchers said. By increasing the scale of the experiment from nano to Lego size, researchers are able to better visualize, describe and ultimately predict the behavior of the particles that normally are far too small to see.

Many designs for nano-devices require the sorting of microscopic particles and ball bearings immersed in glycerin behave much the same way as nano-particles in microfluidic arrays. By determining the likely paths that different sized bearings take on the Lego board, the researchers can predict the paths nanoparticles of different-sizes, charges or textures in the microfluidic arrays.

The team recorded the paths of ball bearings descending through the Lego obstacles and found that the smaller bearings zigzagged randomly through the grid, while the larger bearings followed more deterministic straight lines.

The team's complete results were published the August 14th issue of Physical Review Letters.

Wednesday, August 26, 2009

On a small island in Denmark in the 16th century, a scientific utopia once flourished. Happy farmers tilled the fields in the name of the knowledge and wisdom of their benevolent scientist-lord, who, his eyes constantly fixed on the stars, read the secrets of the heavens night after night. In this small, peaceful kingdom, science ruled, and all were happy.

Well, not quite. Swap happy peasants for terrorized serfs and the benevolent scientist-lord for a drunken egomaniac, and you've got something like a picture of 16th century Hven, a small island in the finger of sea between Denmark and Sweden. In 1575, thanks to a decree by King Frederik, the island came under the sovereignty of one twenty-nine-year-old Tycho Brahe, and life on Hven started to get a whole lot stranger.

Tycho Brahe is one of those historical figures that makes me think, "Gosh, they just don't really make astronomers the way they used to." Forget every documentary you've ever seen that included a pocket-protector wearing NASA astronomer (sorry, guys). Forget your high school physics teacher. I'm convinced that if more scientists got into duels, had fake noses, and just drank as much as Tycho Brahe did, the whole field would look a lot more appealing.

Here's a short bio: Brahe was born in Denmark in 1546 to a noble family whom he annoyed by getting into astronomy rather than law. When he was seventeen, something happened that inspired Brahe to begin taking measurements of the positions of the stars and planets. He saw Jupiter and Saturn pass very close to each other, an event that even the most accurate astronomical tables (of the 16th century) erred by several days in predicting. So he decided he was going to gather his own data.

The whole of Hven became a slave to this this idea, although that was several years later, after he'd studied in Germany, gotten into a duel that cost him the bridge of his nose, and established himself as the premier Danish astronomer. (Which was a higher honor than you might think, since court astronomers were also court astrologers, a handy thing for a king to have around.) When Frederik II gave Brahe Hven as a bribe for staying in Denmark, Brahe constructed a fantastic observatory-cum-palace on the island. He called it the Uraniborg, the castle of the heavens. It cost about 1 percent of Denmark's GDP, greater than the greatest percentage of US GDP that's ever been spent on NASA.

The Uraniborg was outfitted with instruments for observing the heavens; it was an observatory in the days before the telescope. Bringing together a large staff, an army of clocks, and huge, intricately constructed quadrants for providing lines of sight, Brahe could make measurements accurate to one arc-minute (a minute is a sixtieth of a degree.) Johannes Kepler, who worked as an assistant at the Uraniborg, calculating the orbits of the planets, used this data to prove that planets moved in ellipses, destroying the Ptolemaic picture of the universe. But the eccentric Brahe wasn't exactly generous with his data, so Kepler (he admitted this in one of his books) waited for Brahe's death and snatched up the data before Brahe's heirs could realize its significance.

That death is shrouded in a whole lot of mystery. According to legend, Brahe died from a burst bladder after being too polite to leave the dinner table to take a leak. But forensic research on Brahe's corpse, which was interred in Prague, has since turned up mercury in Brahe's hair. In 1996, a physicist at Lund University in Sweden used Particle Induced X-ray Emission to find the location of the mercury in Brahe's hairs, which proved that Brahe had consumed mercury on the day of his death. Was this a case of an an enterprising scientist trying to medicate himself, or was there foul play? A recent book even suggests Kepler poisoned Brahe in order to get at that precious data.

These days, the peaceful island of Hven (now spelled Ven, because it belongs to Sweden) shows little trace of Brahe's strange influence. Brahe reputedly terrorized the peasants (the Uraniborg was outfitted with a dungeon), had a pack of illegitimate children with one of his servants, and got up to mischief constantly with a dwarf court jester and a pet moose who died stumbling down the castle stairs after a night of heavy drinking. While you can't see the pet moose or hear a prophecy from Jeppe the dwarf, you can visit the old grounds of the Uraniborg, see the nearby museum, and have a cup of coffee at the Cafe Tycho Brahe after you've made some observations with a reconstructed sextant and quadrant!

And as if Brahe weren't cool enough, he also coined the astronomical term "nova" when he wrote the treatise "De Stella Nova" on his 1572 observation of a stellar object brighter than Venus - what we would now call a supernova.

Tuesday, August 25, 2009

The wild-haired, frequently sockless Albert Einstein may be the icon of 20th century physics, but there's perhaps no personality in physics more celebrated than Richard P. Feynman. Famously a bongo-player, safe-cracker, and straight-talker, Feynman worked on the Manhattan Project and shared a Nobel prize for discovering quantum electrodynamics, the quantum laws of electromagnetism.

Near the end of his life, Feynman was part of the commission chosen by President Reagan to investigate the 1986 explosion of the shuttle Challenger. During a televised public hearing, he used a C-clamp and plastic cup of ice water to demonstrate that the shuttle's rubber O-rings lost their flexibility at low temperatures.

That was Feynman’s style: no-nonsense, unpretentious, engaging, and powerful. Feynman was a celebrated lecturer; these days you'd be hard-pressed to find a physicist's bookshelf without the three requisite cardinal-red volumes of the Feynman Lectures on Physics, transcribed from his days teaching a two-year introductory physics course at Caltech. Audio of his lectures has also been available for a long time as well; there's something wonderful about hearing the interactions of forces and particles elucidated in the strong dialect of Feynman's native Far Rockaway, Long Island.

Now it's possible for anyone with an internet connection to learn physics with the "curious character" himself. Bill Gates has bought the rights to seven lectures, titled the Character of Physical Law, given in 1964 at Cornell University and recorded by the BBC, and has released them online to the public. (Feynman, though he'd previously been a professor at Cornell, was by this time at Caltech.) The release is a way for Microsoft to show off Project Tuva, an interactive, dynamic media player designed for science content that includes note-taking capabilities and links to outside sources of relevant information – a bio of Danish astronomer Tycho Brahe, for instance, when Feynman mentions him. Otherwise it's chalk and talk, and what wonderful talk

…I'm interested not so much in the human mind as in the marvel of nature, who can obey such an elegant and simple law as this law of gravitation. So our main concentration will not be on how clever are to have found it all out, but on how clever she is to pay attention to it!

The lectures are an unprecedented opportunity to learn physics from one of the most entertaining, brilliant teachers of the last hundred years. (I guess I'll forgive Gates for requiring viewers to download something called Silverlight, which does not like Google Chrome.) If even that requirement offends your tastes, or you're looking for something more advanced once you've visually devoured these seven hours of lectures, try out his lectures on quantum electrodynamics.

Feynman also had a life-long obsession with a little-known kingdom in the depths of the Soviet Union, a place he first discovered via the "wonderful triangular and diamond-shaped stamps" that wended their way from that tiny country to his childhood stamp collections. The Microsoft project gets its name from the same place – Tanna Tuva.

Hypermusic Prologue isn't your average opera. There are no elaborate costumes or powdered wigs, and the plot is hyperreality, not high-brow romantic comedy. That's because the because the person responsible for the lyrics, Lisa Randall, is not your average opera librettist. She's a Harvard University physicist, a celebrated scientist who resides, by profession, on the fraying edges of what we know about the universe. She lives and breathes the p-branes and Anti de-Sitter space-time; her playground requires a huge stretch of imagination for even very smart people to vaguely glimpse, much less participate in.

In a way, her opera seems to be about the loneliness of the theoretical physicist, who creates in a world far removed from what we think of as reality. ("Do I believe in extra dimensions? I confess I do," Randall has written.) Or at least this is the impression I get from SEED:

When the soprano sings, "The scale of my experience is altered," this is partly a literal reference to the way physical scaling changes in Randall’s hidden dimensions. But Ellet is singing to her close-minded partner, baritone James Bobby, who keeps arguing the value of Newtonian physics until he finally has his own brief encounter with her unseen world. In this way, he becomes more open-minded and his perspective is altered.

Randall's also the author of a layman's travel guide to her extra-dimensional universe. Titled Warped Passages: Unraveling the Mysteries of the Universe's Hidden Dimensions, the book introduces readers to the idea that extra spatial dimensions "might nonetheless resolve some of the most basic mysteries of our universe"; perhaps hinting to her lyrical leanings, each chapter is prefaced by a snippet of lyrics from the Beatles, Billy Bragg, Kraftwerk, and Fleetwood Mac. The book convinced Spanish composer Hector Parra that Randall was the perfect librettist for his next opera, and provided the inspiration for the way Parra warps and twists, expands and contracts the performer's voices. Check out the slideshow at SEED for a virtual tour through the opera's abstract stage design (I think NOVA should consider reusing it for their next string theory program) and for musical excerpts.

Our second tale from the world of physics and opera reaches right back to Wagner, who, according to recent digging by some curious physicists, certainly knew his alpha, beta, gammas. Apparently when sopranos try to deliver those really high notes clarity and power, it tends to warp their pronunciation of words. By measuring the vocal tracts of singers as they sang vowels at different frequencies, physicists at the University of New South Wales discovered that, in order to amp up their voices' power, sopranos warp their vocal tract to change its resonant frequency. Here's how it works:

...when a soprano sings at high pitches, she adjusts her vocal tract to make her voice resonate. In effect, she "tunes" the resonance frequency of her vocal tract to match the frequency of the pitch at which she is singing.

According to the abstract of the paper in the Journal of the Acoustical Society of America, the result is that vowels, "move, converge, and overlap their positions on the vocal plane...to an extent that implies loss of intelligibility."

Here's where Wagner came in.

One of the study's leaders, John Smith, was sure that a genius like Wagner would be able to find a way around this physiological physics problem, by writing a libretti such that the vowels would match the pitch at which they would be sung:

So one evening in his garden while he was recovering from surgery, Smith took up a pen and paper and went through Götterdämmerung note-by-note, lyric-by-lyric, recording which notes were paired with which vowel sounds. In the early hours of the next morning he wrote a computer program to determine with statistical certainty whether Wagner had in fact used a vowel-pitch matching technique. Looking at the program’s first results, he was amazed. There was a clear relationship.

Meanwhile, Rossini, Mozart, and Strauss's works showed no such relationship. But Wagner couldn't have grasped the "soprano problem" in the technical way the University of South Wales physicists did, which leads us to believe he solved the problem intuitively, just as the Alhambra probably wasn't built as a shrine to mathematical symmetry, despite the fact that its mosaics exemplify it beautifully.

For the last word on physics and music, some lighter fare. I've been looking for an excuse to talk about Rhythm, Rhyme, Results, a company that brings together some pretty legit-sounding lyricists and rappers to pen and perform rap songs about geometry, geoscience, and physics (equations and numerical facts included) that I wouldn't be ashamed to blast on my car stereo.

Friday, August 21, 2009

Most fire codes require that the pathway to an emergency exit be kept wide open, but according to researchers in Japan, placing an obstruction next to an exit may actually help crowds of people to get out of a room more efficiently.

Researchers found that when people bottleneck near an exit, they start to jostle each other for position. The jostling acts much like friction, slowing down the rate at which people can exit. Introducing a strategically-placed obstacle near the exit can reduce the number of people pushing for the exit, speeding up the rate at which people can pass through.

"We found that we can evacuate faster if we put an obstacle at the suitable position in front of the exit," said Daichi Yanagisawa, who lead the study from the University of Tokyo in Japan.The researchers started their study by having large simulated crowds of people bottleneck around small exits, and then introduced obstacles that everyone would have to avoid in order to reach the exit. Most of the time, the obstacles reduced the number of people able to exit per minute. Surprisingly, they found more people could escape in less time if an obstacle was placed about 30 degrees to either the right or left side of an exit door.

"Contrary to our intuition, the obstruction by the obstacle increases the pedestrian outflow in a certain case, since it decreases conflicts among pedestrians," Yanagisawa said.

Researchers found that having an inanimate pole take up the space of a person reduced the number of time-consuming conflicts between people near the exit. Similarly, the pole's placement slightly off to one side of the doorway reduced the time it took for a person coming from the other direction to turn toward the exit.

To test their results, the researchers went to the studio of a local TV station and watched 50 volunteers exit through a narrow door. They found that the crowd of real people closely mirrored the researcher's previous computer predictions. Likewise, when they placed a pole to one side of the exit, the people were able to exit faster than when there was no obstruction at all.

Yanagisawa's team was the first to put this into mathematical terms.

"I believe that our work will help design better and more efficient fire escapes since our model gives us the value of pedestrian outflows based on both theoretical and experimental study," Yanagisawa said.

During the experiment, the team also found that people exiting in a single-file line were by far the most efficient. Yanagisawa said that the next step is to program models of people intelligent enough to self-organize into a line.

Thursday, August 20, 2009

The holy kilogram, under its three bell jars at the Bureau International des Poids et Mesures

If there's anything one can depend on in this changing world, it's physical units. The kilogram, meter, and second have stood me in good stead since elementary school. But according to an NPR report on the radio this morning, the tried-and-true kilogram may be changing. That's because it's defined as the mass of an actual lump of metal, guarded by the high priests of the Bureau International des Poids et Mesures. Before continuing, I recommend you listen to the report (it runs about five minutes. You can also read the written story at NPR.

To quote Brumfiel's article:

As it stands, the entire world's system of measurement hinges on the cylinder. If it is dropped, scratched or otherwise defaced, it would cause a global problem. "If somebody sneezed on that kilogram standard, all the weights in the world would be instantly wrong," says Richard Steiner, a physicist at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md.

So the fate of all we hold dear depends on a few atoms crusting off a century-old platinum-iridium alloy salt shaker in a bell jar outside of Paris? How did we get ourselves into this mess?

To be fair to SI, the kilogram seems to be the only weak link in the seven fundamental units of the metric system. The rest--metre (length), second (time), ampere (current), kelvin (temperature), mole (amount), and candela (luminous intensity)--can all be derived from lab measurements of physical phenomena or substances. A mole is the number of atoms in 0.012 kilogram of carbon 12; the kelvin is 1/273.16 of the thermodynamic temperature of the triple point of water.

I'll focus now on the meter and the second, being a little closer to home than the candela or ampere. Upon examination, it's not so suprising that the kilogram is changing; really, it's just catching up with the meter and the second, which have steadily evolved over the last hundred-plus years.

The meter was originally defined as one ten-millionth of a quadrant, the distance between the Equator and the North Pole, based on a measurement taken in the 1790s (it's off by .02 percent). When the kilogram was forged in 1889, a platinum-iridium meter was made as well. The first Conférence Générale des Poids et Mesures announced, "This prototype, at the temperature of melting ice, shall henceforth represent the metric unit of length." The meter still sits somewhere deep in the bowels of the BIPM, perhaps somewhere in the region of the goblin carts and fire-breathing dragons.

At the 11th CGPM in 1960, the same year that the metric system was given the name SI and adopted as the official system for scientific measurement, the meter was redefined in terms of the wavelength of krypton 86 radiation. This definition lasted a mere 23 years, when this was scrapped (lasers being more dependable than radium) for how far light travels in a vacuum in 1/299,792,458 of a second. (Recognize that funny number? It's the speed of light.)

Similarly, the second has undergone a few changes over the years as well, and it's still evolving. Originally it was determined as a tiny fraction of a solar day, until astronomers realized the length of a day wasn't constant. So they hit on defining the solar day as January 1, 1900. While this is sort of cute, there are some inherent problems. As Russ Rowlett puts it in his online Dictionary of Units of Measurement, "Since we can't go back and measure that day any more, this wasn't a real solution to the problem."

So another resolution was issued in 1967 by the all-powerful Wagamumps of the CPGM:

The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

This means that anyone with the right equipment could measure the second. In the United States, the wonderful people at the National Institutes of Standards and Technology in Boulder, Colorado take care of this for us with the NIST-F1 cesium fountain clock:

The fountain, in this case, consists of six infrared laser beams and a cloud of cesium atoms in the clock's vacuum-chamber gut. The laser beams clump the cesium into a ball that's nearly at 0 kelvin. This ball then rides upward on the "fountain" of two vertical lasers into a microwave cavity. As they rise and fall, some of the cesium atoms fluoresce; the clock keepers tune the microwave radiation until it maximizes the fluorescence. And this magic frequency is 9,192,631,770 Hz, the resonance frequency of cesium.

If anything, today's NPR story reminds us of how units of measurement are totally arbitrary and yet absolutely necessary. Without them we can't build anything or buy anything, and we certainly can't do science. So humans began casting about for a way of parceling out grain, land, and stone since we first started trading and building. The dimensions of the Pyramids, architectural wonders that they were, were measured in the meh, a variation of the cubit, a unit popular in the ancient world based on the length of the forearm from elbow to middle finger. (The meh was a "royal cubit," which added the width of the palm of the current Pharoah.)

It seems not much has changed since those days, because the Egyptians, like the French in 1889, constructed a standard for the cubit, a length of granite preserved with a fierceness to rival even the BIPM. Architects and builders made yardsticks based on the cubit rod, and brought them back periodically to make sure they didn't deviate too far from the cubit. This was good enough to build structures that have lasted for thousands of years.

A wooden cubit rod belonging to Tutankhamen's treasurer, preserved at the Louvre

Creating a standard of measurement is universal through human civilizations, no matter where or when they sprouted up. (More recently, the Swedish used the .593-meter-long Rydaholmsaln, based on a prototype kept in the church porch of Ryadholm, Småland.)Figuring out a new measure for the kilogram might be a monumental task, but at least we're not forced to measure our gas mileage in tlacaxilantlis per cwierc.

Wednesday, August 19, 2009

WFPC 3 shaking in its boots, awaiting cosmic radiation in the bowels of the Space Environment Simulator.

Yesterday I blogged about seeing the Hubble Wide Field and Planetary Camera 2, which, after astronauts replaced it with the WFPC3, came home with the Atlantis shuttle in May. But there's a lot more to the building it's in, which has the predictably unfathomable name "the Integration and Test Facility." Built during the space race, the I&T is a palace of wonders. Our guide, Aleya, works on education and public outreach for the Solar Dynamics Observatory. She's used to taking legions of kids through the facility, talking about possible careers—NASA employs seamstresses as well as rocket scientists—and filling them with facts about the facility's impressive array of, well, tools, for lack of a better word. Take the Space Envinronment Simulator:

Goddard's Space Environment Simulator.

Its crown scrapes the 30-foot ceiling of the I&T facility; there's another 30 feet of it underground, 10 feet of chamber and twenty feet of foundation capable of supporting 4,000 pounds. Scientists gingerly lower space-destined equipment, such as a new satellite, into the UFO-like structure. Then they close the door and, or so I'd assume, press the big red button labeled "SPACE," which turns on the high vacuum, chilly (-310 F°) or blazing (340°) temperatures, and even cosmic radiation, high-energy protons, neutrons, and nuclei.

Looking into the centrifuge.

Just beyond these massive doors lies the centrifuge. The 120-foot-long rotating arm can spin up at up to 33 RPM and generate up to 30 Gs of acceleration. Aleya jokes that it's Goddard's biggest storage closet; at the moment the floor is cluttered with mysterious equipment, but just a few months ago the new Hubble camera, the Wide Field and Planetary Camera 3, was put through its paces here. But this is not a training ground for astronauts; 30 Gs is far beyond what the human body can withstand.

"It takes about a gigavolt to start it up," Aleya says. Thats a thousand million volts. Phew. Wonder if the neighbors notice.

Finally we came to a room that looked straight out of either a modern art museum or from an episode of Cribs:

The bottom half of the subwoofer...

One of the Acoustics Chamber's 42 foot walls is one massive subwoofer, the world's biggest. Each speaker is 6 feet tall. The tweeter, on the other side of the room, is big enough to crawl into. Like everything else at the I&T facility, this feels like something designed by a giant. It's here because space scientists really do have to think of everything. Equipment that goes to space has to endure incredible hardships, including the deafening roar of launch. If you were unfortunate enough to be caught inside this room once the iron doors slowly swing shut, it would be like standing right under a rocket during lift-off. 150 decibels, baby.

...and here's the tweeter. Moments later we recreated the RCA logo.

"Rumor has it that the paint peels off, but I've never seen them repainting," says Aleya.

If you enjoyed our mini-tour of Goddard, you have to watch this grunge music-infused NASA video chronicling WFPC 3's trial by fire through the I&T facility's series of escalating "tortures." You'll see the acoustics chamber and centrifuge in action, and watch the massive hatch close over the Space Environment Simulator.

Special thanks to Aleya Van Doren for taking us on this tour of Goddard. If you're an educator or a student, check out her outreach page for ways to use NASA SDO materials in the classroom.

Tuesday, August 18, 2009

Seeing the Hubble's Wide Field and Planetary Camera 2 last week is like visiting an old and venerable explorer just back from a long and exhausting expedition. The camera, which flew back from orbit this May in the payload of the Atlantis Shuttle, was sitting in a spacious, stark-white clean room on the campus of NASA Goddard Space Flight Center. Although it weighs 610 pounds—NASA writers often compare it to a baby grand piano—it was dwarfed by giant chunks of the space shuttle's payload, including the circular catching mechanism that grasped the telescope.

Pieces from Atlantis's payload that cradled new instruments and caught Hubble.

If I could look inside the camera—unfortunately, a healthy layer of cleanroom glass separates me from it—I'd see four tiny mirrors, each the size of a nickel. These mirrors were replaced in the WFPC2 ("whiff-pick two," for the cool kids) before it was flown up to Hubble in 1993, taking the place of the first camera. The mirrors offset a spherical aberration in Hubble's main 8-foot mirror, an aberration that cost Hubble's photos their clarity for the first three years of its life. Since then, WFPC2 has snapped over 135,000 close-ups of the universe's beauties, and it doesn't look the worse for wear, except for a few dings in its cover from meteorites. Like most of what's come back from space, the venerable explorer will find its way from its current spot, just around the corner from the cleanroom where it was assembled, to the Smithsonian's collection.

Goddard had an important role in the recent servicing mission. It has replicas of all three pieces of the massive Hubble—the telescope portion alone is bigger than a bus, and the electronics and instruments cabinets are similarly gargantuan. Familiarity with the wildly unfamiliar is key to getting anything done in space, STS-125 astronauts trained extensively on the replicas before the mission. Goddard's engineers designed repair tools that made up for the ungainliness of space suits—you try turning a screwdriver while wearing a stiff inflated glove!—and prevented loose screws from floating into space.

A replica of Hubble's fuse box. It took astronauts twelve hours to change these fuses.

A Hubble tool - I wonder what this does?

This face plate fit over an especially intricate panel to catch loosened screws.

Monday, August 17, 2009

Most of us think of Science as a generally dignified enterprise. You plan your procedure meticulously, set up your instrument, conduct your experiment methodically and calmly, then write up the results. You don't shout and curse as your precious telescope bangs into the truck that's carrying it as you try to launch it into the sky. Right?

The above clip, from last Thursday's episode of the Colbert Report, contains footage from BLAST, a documentary by filmmaker Paul Devlin. Devlin didn't look far for the subject of his film--the story follows the daily life of his brother, Mark Devlin, the guest in the above clip. Which meant traveling to Arctic Sweden, Canadian polar-bear country, and, finally, Antarctica.

Based on where his work has taken him, you might guess that Mark is an explorer. In a way, he is.

He's an experimental cosmologist at the University of Pennsylvania, and he's trying to figure out what the universe looked like just after it was born. For that he needs old light, light that's been traveling for over 10 billion years, carrying the signature of the universe's infancy. The oldest light in the universe is called the cosmic microwave background. Emitted just a few hundred thousand years after the big bang, the CMB, (scientists love their acronyms) is a 3 kelvin microwave bath that's nearly uniform throughout the entire universe, right down to 1 part in 100,000. But these tiny inconsistencies speak volumes about the early universe and our own origins.

Although this radiation has mostly cooled down to the microwave region of the electromagnetic spectrum, dust from early galaxies absorbed the energetic ultraviolet and optical light of the brightest stars and re-radiated the thermal energy at infrared wavelengths. So Mark Devlin spearheaded BLAST, the instrument who shares its name with the documentary's title, to study these infrared signals. BLAST stands for "Balloon-borne Large-Aperture Submillimeter Telescope." Submillimeter because it looks at photons with wavelengths between 250 and 500 micrometers, an order of magnitude shorter than a millimeter. Balloon borne because the team cradled the telescope in a large gondola and rigged it up to a NASA long-duration balloon, an ethereal-looking helium balloon that sailed it up 120,000 feet into the air - that's about 4 times the altitude of Mount Everest's peak. While still in the stratosphere, the telescope is above most of the atmosphere's particles, meaning photons have a clear path to its detectors.

The team of physicists and grad students behind BLAST launched the telescope once in New Mexico for a test run, then again north of the Arctic Circle in Sweden, again in Canada (according to the movie website, though I can't find any information on it; apparently it was a failed flight), and then a final time, in Austral summer 2006, in Antarctica. I've linked here to the blog of one of the project's graduate students, Don Wiebe, who documented each launch—and the life that went on between them— in photo blogs. (The photo below is from his blog) Graduate student Gaelen Marsden also kept a photo blog: here's his day in the life of an Antarctican long-duration balloon scientist.

Friday, August 14, 2009

Everyone's heard of Hans Christian Andersen, the Danish author of classic children's stories like "The Little Mermaid" and "The Ugly Duckling." But if you were wondering about the significance of today's Google logo, you probably don't know that today is the 232nd birthday of another Hans Christian, a physicist who changed the way we see electricity and magnetism.

Hans Christian Ørsted didn't pen any fairy tales, although he was a contemporary of Andersen, who fell in love with Ørsted's daughter for a period. But he did work in a field that mystified most people in the 19th century. One evening in 1820, Ørsted was preparing a lecture for his class at the University of Copenhagen when he noticed something unusual. As he set up a demonstration with a live wire, he saw that the needle of a compass that happened to be sitting on his work table jumped away from north, tugged by an invisible force. Then Ørsted knew: electricity and magnetism were not separate phenomena, as physicsts thought. The current through the wire was creating a magnetic field. This was 11 years before Faraday's induction experiments and the birth of Scottish physicist James Maxwell, who would write the laws governing electromagnetism.

Ørsted was rewarded for his discovery by immortality in the form of a park in Copenhagen that bears his name. Physicists also gave units for magnetic field strength his name, but the oersted died out in the fifties when the SI system replaced the old CGS system, based on the centimeter, gram, and second. (Now we base things on meters, kilograms, and seconds, although there is no SI equivalent of the oersted.) Luckily, his name was resurrected again when the Danes launched their first satellite in 1999. Appropriately enough, Ørsted's mission was to precisely map earth's magnetic field.

Given that Ørsted's been dead two centuries, I don't mind bringing up this alternative version of the story of the physicist's accidental discovery, which comes from the UCLA physics department Web site:

Often during his lectures at the University of Copenhagen H. C. Oersted had demonstrated the non-existence of a connection between electricity and magnetism. He would place a compass needle near to and at right angles to a current carrying wire to show that there was no effect of one on the other. After one of the lectures a student asked, "but, Professor Oersted, what would happen if the compass needle was placed parallel to the current carrying wire?" Oersted said, "Well, let's see," and went down in the history of physics; the student's name is forgotten.

Thursday, August 13, 2009

Snap, crackle, pop. The world is alive with invisible magnetic field lines. Take a length of wire with a current running through it; it generates a magnetic field that curls around the wire, but we can't see it.

Video artists Ruth Jarman and Joe Gerhardt, who work under the moniker Semiconductor, shot footage of empty lab space at UC Berkeley's Space Science Laboratory. Then they brought the inanimate objects to life, painting in the vivacious spaghetti of magnetic field lines coming off the unassuming electronics. The pair, who hail from London, spent four months "researching and experimenting" at the northern California lab, which tackles a smorgasbord of space physics topics, from the search for extra terrestrial intelligence to solar flares. One might say that the scientists were "researching and experimenting," and that the artists were watching. Or one might say that Semiconductor's appropriation of raw satellite data of coronal mass ejections was a form of data processing, and that when they videotaped the lab's scientists trying to answer one very tough question, they were trying to prod the borders of science's domain.

I should warn that Semiconductor's magnetic field lines, while certainly beautiful (especially with all the added space-noises!) are not what the field lines of these objects actually look like. (The scene with the wires is the biggest give-away.) But I think the artists skillfully evoke this invisible force, even if they're not portraying it in a way true to nature. Think impressionism rather than realism.

I found the inaccuracy a little disappointing until I found SSL's website for IMPACT, a suite of instruments that collect data about solar wind electrons and the sun's fluctuating magnetic field. IMPACT is part of STEREO, two space craft, one in front of the earth and one behind, that monitor the sun's storms. If you watch the videos on the STEREO site (the introduction is a good one), it seems like Semiconductor were drawing their inspiration from the "hairball" of magnetic field lines on the sun, and the violence of coronal mass ejections, hot balls of plasma the sun fires toward earth on occasion. Another fun resource are these animated models on the IMPACT page, which raises the question again - Who are the artists here and who are the scientists?

Semiconductor's animations are inspired by some really interesting science, but wouldn't it be cool to see what magnetic field lines actually look like? Check out Falstad.com, the Disneyland of physics computer applets, which has a great little widget that allows you to see the magnetic fields and vector lines of some common configurations like a current-carrying wire, a loop of current, or an electromagnet. You can move your wire around, change the strength of the field, or sprinkle the air with tiny current carrying loops and see what happens. Just make sure to read the directions!

Although the show started last night, tonight you can catch the grand finale of the biggest heavenly event of the summer: the Perseid meteor shower. As earth travels in the Swift-Tuttle comet's dusty wake, the night sky reveals us caught in a fire storm of ice-bound dust sizzling in our atmosphere. We call these "shooting stars" the Perseids because they seem to emanate from the constellation Perseus, named after the hero from Greek mythology who slew Medusa. Look for them streaking out from the northeast part of the sky near a Y-shaped constellation.

According to a late report from National Geographic, the Perseids are even showier this year because of a distant friend in the solar system—Saturn. As Swift-Tuttle swung by the giant a few years ago, Saturn's gravity clumped a portion of its tail together. Tonight we'll be cruising through the thick of the meteors, so you'll be seeing up to 100 meteors an hour. Great news for people with short attention spans, like your blogger.

There are three things that might get in the way of your meteor-viewing: the moon, light pollution, and clouds. The moon was full just a few days ago and is still pretty fat, so its light will make the Perseids harder to see if you're in North America. If you're contending with blazing streetlights, as someone who grew up thinking there were four five stars in the entire universe, I sympathize.

Consider planning a trip to a national park for next year's shower. I know, I know, I hate hiking, too, but national parks preserve something that, these days, is as rare as untouched nature – dark skies. In fact, national parks are such a resource for amateur astronomers that University of Redlands astronomy professor Tyler Nordgren spent a year touring the skies of twelve national parks, from Denali in Alaska to Acadia in Maine. If light pollution is drowning out the show, troop back inside, fire up the old computer, and check out the blog of his journey, which reads like a sort of nerd's travel guide to the American great outdoors. (And includes great photos, like this one from Bryce Canyon National Park in Utah)

Another option for those contending with cloudy skies is to sit back with this gorgeous Hubble video. By pointing the Advanced Camera for Surveys at apparently black space and letting distnat light fall on the sensor for ten days, astronomers were able to peer deep into the universe to create what's known as the "Hubble Ultra Deep Field," an image swimming with distant galaxies. The red-shift of the light from these galaxies gives away how far from us they are. Add some ethereal opera music and computer magic, and voila! A simulated 3-D fly-through of a universe so densely populated with galaxies it's absolutely mind-boggling. So you can tell your lucky friends in places like, say, rural Arizona, that meteors are so August 12 - galaxies are more your taste, thank you very much.

Tuesday, August 11, 2009

Visit Tiffany Ard's Web site, and you'll see ABC and number cards for babies, a children's book, and nursery prints, all rendered in the beautiful, whimsical watercolors you might expect from a children's artist. But within seconds of browsing the site, you'll realize there is something very, very strange going on here.

"I have a really weird sense of humor," Ard says. Her tongue-in-cheek products for "nerdy babies" take the parenting obsession with educational products like Baby Genius and Baby Einstein "to its logical extreme," she says. She puts on a hilarious mock coo. "So H is for hydrogen bonding, and you have to know that, baby."

While even the most precocious of babies might be a few years and physics classes short of appreciating her artwork, nerdy parents love it. So much so that what started out as one-time present for a nerdy friend's baby shower is now a budding business, which Ard, formerly a commercial artist working in software marketing, supports from her home near Atlanta while raising a family with her husband, artist Kevin Ard. Her blog is a hilarious account, complete with scientific graphs and flowcharts, of her life as nerd, artist, wife, and mother of two very small, very inquisitive boys. From how much it makes me laugh, I'd say that life at Chez Ard seems best described by throwing the words domesticity, chaos, and happiness into a blender set to "frappe."

Because her business is entirely online, Ard has let customers have had a hand in her growing line. She painted her latest piece in response to the geologist contingent, who felt underrepresented in her oeuvre. She's also heard her share of that favorite phrase of scientists, "Well, technically..."; she even has a series of products based on it.

"One great thing is I sell to nerds, and they are really quick about correcting me," Ard says. One of her prints, a painting of a tortoise with the Magritte-referencing phrase, "Ceci n'est past une turtle," incited a massive Linnaen debate over whether tortoises and turtles were the same animal. "Holy moly, turtle people are crazy!" Ard says, laughing. She turns, again, to her sense of humor to find an answer. "My husband says, 'It's still not at turtle. It's a picture of a turtle.' "

One of Ard's first paintings depicts a little girl standing in the tide under a full moon, just the sort of painting you'd expect in a kindergarten classroom. But the unexpected subject of the girl's childish ruminations isn't the flowing sea or a falling star, but the inverse-square law of gravitational attraction:

"It's like a litmus test to find out if your friends are nerds," Ard explains. If you saw the painting in a friend's nursery from far away, she says, you'd have certain expectations.

"[You'd think], oh, it's probably...'reach for the stars, little girl', and then you read it, and you're like, 'Oh wow, these people are awesome, or terrible nerds.'" Her other astronomy painting takes its inspiration from her college astronomy class.

Boundaries between science and art seem to be fluid for Ard, who claims she always knew she wanted to be an artist, but at the same time always had a fascination with science. She credits her "Renaissance man" father, a pilot, violin maker, machinist, writer and artist.

"It was never presented to us that there are these lines between one field or any other," Ard says. "It wouldn't occur to me that physics is walled-off for people who don't know about it."

Maybe that's why she draws freely from math and science for her nerd-delighting artwork. Her easy traversal of the line between art and scientific ideas landed her an invitation to SciFOO, a "Unconference" hosted by Google and organized by IT publisher O'Reilly and the Nature publishing group. One of the running topics for the Unconference was getting the public interested in science.

"It's kind of a weird conversation for me," she says. "At least for kids, that's like sitting around talking about, 'How do we get our puppies more interested in chewing?' That's all they do. Even grownups are interested in science if you can convince them they're allowed to be." We hope you let Ard's artwork convince you.